/**
* @ProjectName: ShopSytem
* @Title: ImageCode.java 
* @Package com.element5th.shop.servlet 
* @Description: 用于产生图片验证码
* @author 第五元素小组   
* @date 2012-10-26 16:06:46 
* @version V1.0   
*/
package com.element5th.shop.servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * Servlet implementation class ImageCode
 */
@WebServlet({"/image_code", "/page/admin/image_code"})
public class ImageCode extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
	private Random random = new Random();

	/**
	 * @see HttpServlet#service(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setHeader("Pragma","No-cache");
		response.setHeader("Cache-Control","no-cache");
		response.setDateHeader("Expires", 0);

		// 在内存中创建图象
		int width=60, height=20;
		BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

		// 获取图形上下文
		Graphics g = image.getGraphics();

		// 设定背景色
		g.setColor(getRandColor(200,250));
		g.fillRect(0, 0, width, height);

		//设定字体
		g.setFont(new Font("Times New Roman",Font.PLAIN,18));


		// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
		g.setColor(getRandColor(160,200));
		for (int i=0;i<155;i++)
		{
		  int x = random.nextInt(width);
		  int y = random.nextInt(height);
		  int xl = random.nextInt(12);
		  int yl = random.nextInt(12);
		  g.drawLine(x,y,x+xl,y+yl);
		}

		// 取随机产生的认证码(4位数字)

		String codeList = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";

		String sRand="";


		for (int i=0;i<4;i++){
		int a=random.nextInt(codeList.length()-1);
		  String rand=codeList.substring(a,a+1);
		  sRand+=rand;
		  // 将认证码显示到图象中
		  g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
		  g.drawString(rand,13*i+6,16);
		}
		
		HttpSession session = request.getSession();

		// 将认证码存入SESSION
		session.setAttribute("rand",sRand);

		// 图象生效
		g.dispose();

		// 输出图象到页面
		ImageIO.write(image, "JPEG", response.getOutputStream());
	}
	
	/*给定范围获得随机颜色*/
	private Color getRandColor(int fc,int bc){
		  Random random = new Random();
		  if(fc>255) fc=255;
		  if(bc>255) bc=255;
		  int r=fc+random.nextInt(bc-fc);
		  int g=fc+random.nextInt(bc-fc);
		  int b=fc+random.nextInt(bc-fc);
		  return new Color(r,g,b);
	}

}
